Preparation of high alpha cellulosic pulp



Patented Dec.'29,.1931

' -UNIT D; STATES PATsNT. orator:

nron nnannm'e, or nnnvnznn, rLLmo'Is, assmnon to coans'rm ama commnv,me, or JJANVILLE, rumors, A conronazrron or nnmwmn ranranurro vor menALPfiA onnnunosrc rune No Drawings Application filed March 31,

The present inventlon relates to an 1mprovement in the process ofmanufacturing high alpha'cellulose.

One of theobjects of the invention is to provide a ravV material for themanufacture of high alpha cellulose which, when subjected to thetreatment as laid down in the co-pending application, will be productiveof a cellulosic product running uniformly from. 95 to 96% ofalphacellulose.

Another object of the invention is'to treat cellulose of the; typederived from plants of annual growth such as cornstalks, bagasse, straw,sorghum stalks, etc., under pressure with water so as to form a rawmaterial more particularly suitable for conversion into high alphacellulose in accordance withthe process described in the said coendingapplicaalkali-soluble" constituents of the cellulose leaving thehigh-alpha-cellulose in substantion and which process is su stantiallyas described hereinbelow. Q

A further object is to produce cellulose yielding a softer and moreuniform aper.

\ Cornstalk cellulosepulp, after beaching and in thecondition in whichordinarily it would be .ready for conversion into paper pulp or paper,is subjected tofa solution of sodiumhydroxide having a sodium hydroxidecontent of from 4 to 6% (4 to 6 grams per 100 cubic centimeters ofsolution); The temperature at which the/cellulose is treated ispreferably near the freezing point. The sodium hydroxide solution ma Ibe used for repeated lots of cellulose until its specific gravity hasincreased to 1.97 5.

The solutionwill take up xylan and other tially pure form. 1

In the said 'co pending application, the results of a series'ofinvestigations which may be summed up as showing that the best resultsare obtained for commercial purposes at telnperatures between zero to 10centigrade with aninitial concentration of 6 grams of sodium hydroxideper 100 c. c. of solution.

The alpha cellulose products, by the said process, average from 94to 96%of actual but'it'has been found occasionall that despite allprecautions, instead of o taining a maximum of 96%, the product will befound carried out as follows:

- hereinabove described.

"words, boilin v moves some 0 the constituents of the cellulose 1930.Serial No.

lulose. Y

L Inasmuch as alpha cellulose is sold to specification, and the usethereof depends =11 on' the uniformity of the said alpha cellu osocontent, the present process was devised in order to insure a rawmaterial which would imiformly give the desired high'alpha cellu- Theprocess of the present inventibncomprises the treatment of cornstalkcellulose with water, under pressureand heat, and is The cornstalkcellulose nlp, already bleached. and ordinarily rea y to be -convertedinto pa er ulp or paper, is placed in a digester, pre era ly of thecirculatmg typefi together with sufiicientwater to forma-readily flowinpulp, and heated therein, until the water, is brought to the boiling intand "(g .an internal pressure of 5 pounds a ove that over theatmosphereis developed. This boilf ing of the cellulose in the water,under pres sure, is continued for about one hour, at the (end of whichtime the contents of the digester are dischar ed and the cellulosefiltered therefrom and t en subjected to the alkali treatment,i 1accordance with the process invented by me and James S. Sconce, aslaid'down in the aforesaid co-pending application and as It is foundthat high alpha'menulose pr-e;

pared b the already mentlonedproces and from ce lulose treated inaccordance with the present invention, yields a pulp' which, when madeinto sheets',[shows a ver low degree of hydration and yields a mucsofter paper,

having a higher" tearing strength; in other I under ressure-in waterrewhich interfere with the perfect operation of high alpha celluloserecess disclosed in cm a pending application erial No. 385,061. The

recess is also applicable to cellulose .to lower its degree of hydrationso'that a softer paper results; f

What I claim' and desire to protect by Letters Patent is:

1. The process of' conditioning cellulose derived from plants-"of annual'growth,-for I the manufacture of high alpha cellulose therefrom whichcomprises subjecting said cellulose in thebl'eached condition to theaction ofwater under pressure and heat.

2. A process as defined in claim 1, wherein the temperatureds equivalentto a pressure of pounds super atmospheric.

3. The process of conditioning cellulose which comprises subjecting thesame, after bleaching and washing, to the action of water under heat andpressure,

4. ,The process of treating bleached cornstalk cellulose which comprisesplacing the same into a digester together with water and thereuponsubjecting the contents of the digester to heat sufficient to boil thewater until the pressure in the digester rises to substan: tially fivepounds above atmospheric, and maintaining said pressureby he'at'forabout one hour, and thereafter releasing the pressure and separating,the cellulose from the water.

In witness whereof, I have hereunto subscribed my name.

ELTON DARLING.

